JPH093032A - Integrating method for ammonia/urea - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for joining ammonia to urea capable of reducing energy and investment.

SOLUTION: An ammonia/urea joining plant comprises an ammonia synthesis gas apparatus 26 for reacting a hydrocarbon supplying raw material with steam and air to form a CO₂ gas flow and a synthesis gas supplying flow composed of hydrogen and nitrogen, an ammonia conversion apparatus 78 for blending a recycling flow with the synthesis gas supplying flow, sending the mixture to an ammonia synthesis reactor, recovering and ammonia flow and a purging flow and forming a cycling flow, a urea apparatus which is a urea apparatus for reacting a CO₂ flow with the ammonia flow in the presence of oxygen for passivation and a small amount of nitrogen under relatively high pressure and forming urea and comprises a high-pressure cleaner 144 for separating oxygen and nitrogen from a urea-containing flow and forming a high-pressure nitrogen flow containing a small amount of oxygen, CO₂ and ammonia and being higher than 14MPa, and a conduit for introducing the high-pressure nitrogen flow to an automatic thermal reformer 36 by compressed air.

COPYRIGHT: (C)1997,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to integrated ammonia /
More particularly, it relates to an ammonia / urea integrated process in which a purge stream from the urea process is fed as a feedstock for the ammonia process.

[0002]

The use of air to prevent corrosion in the urea process is known in the art, but the oxygen contained therein passivates the metal surface of the device. In most cases
It is also well known that the CO ₂ feed fed to the urea process contains hydrogen and nitrogen. CO supplied to the urea reactor
₂ Air is typically added to the feed. In some urea process, hydrogen contained in the CO ₂ feed is reacted with oxygen in the air injected into the process. Alternatively, hydrogen remains in the process, leaving one inert that must be expelled from the process along with nitrogen and other inerts from the air.
In the integrated method, a portion of the high pressure air compressed for synthesis gas production in ammonia production is diverted for metal passivation in urea production. It will be appreciated that large amounts of inerts in the reaction feed stream must then be driven out of the reaction effluent stream.

The high pressure vapor purge stream removed from the urea synthesis reactor also contains unreacted carbon dioxide and ammonia. Such a residue is substantially absorbed as carbamate in a scrubber operated with synthetic circulating pressure using carbamate wash water. The purge vapor, which consists of mostly nitrogen and residual ammonia, taken out from the high-pressure washer,
Generally, the pressure is reduced to an intermediate pressure absorber. Intermediate pressure absorbers use plant condensate scrubbing to reduce the residual ammonia concentration in the purge vapor to a level suitable for release to the atmosphere.

[0004]

The need for the equipment required to avoid depressurization of the high pressure urea synthesis purge stream and to discard and remove residual ammonia to the atmosphere in connection with energy and investment savings. It would be advantageous to eliminate

[0005]

The high pressure purge gas removed from the urea synthesis cycle is recycled to the air supply conduit upstream of the autothermal or secondary reformer of the ammonia plant. In this way, a portion of the air feed to the ammonia synthesis cycle is supplemented with urea purge gas to conserve the compression energy of the air compressor and to remove the ammonia to clean the urea purge stream for disposal to the atmosphere. Equipment can be unnecessary.

In a first aspect, the present invention provides an integrated ammo
Provide near / urea plant. Hydrocarbon feedstock and steaming
Reacts with air and air to produce CO_TwoFlow and hydrogen and nitrogen
In series to form with syngas make-up stream containing
In addition, primary reformer and automatic thermal reformer, shift converter, coagulator
Condense stripper and CO_TwoAmmoni with removal device
Install a syngas device. Ammonia containing synthetic pathway
A converter is installed to mix the recycle stream with the syngas make-up stream.
To form an ammonia converter feed stream. In addition,
The ammonia synthesis route process requires the ammonia converter supply logistics.
Send to ammonia synthesis reactor, effluent from synthesis reactor
Ammonia flow is recovered from the
And recovering and forming a recycle stream. urea
The device should be deployed to provide a passivating effective amount of oxygen and a small amount of
CO at relatively high pressure in the presence of nitrogen _TwoStream and ammonia stream
React to form urea. Urea device is a urea-containing flow
Oxygen and nitrogen are separated from the_Twoas well as
High pressure to form a high pressure nitrogen stream containing ammonia
Has a washer. Automatic thermal reforming of high pressure nitrogen stream with compressed air
Provide a conduit for introduction into the vessel.

The high pressure nitrogen conduit preferably communicates directly with a compressed air conduit downstream of the air compressor, the pressure in said high pressure nitrogen conduit being greater than the pressure of the compressed air conduit. The urea unit preferably has no ammonia removal equipment to treat the high pressure nitrogen stream and no vent to atmosphere for nitrogen from the high pressure washer.

In another aspect, the present invention provides a method for integrating the operation of an ammonia plant and a urea plant. The ammonia plant reacts the hydrocarbon feedstock with steam and air to form a CO ₂ stream and a syngas make-up stream containing hydrogen and nitrogen, in series, with a primary reformer and an autothermal reformer. quality device, a shift converter, having a condensate stripper, and ammonia synthesis gas system comprising CO ₂ removing device. The ammonia converter mixes the recycle stream and the syngas make-up stream to form an ammonia converter feed stream, which feeds the ammonia converter feed stream to the ammonia synthesis reactor and the effluent from the synthesis reactor. From the effluent stream and a purge stream from the effluent stream to form a recycle stream. Urea plants have a urea unit that reacts a CO ₂ stream with an ammonia stream at relatively high pressure in the presence of a passivating effective amount of oxygen and a small amount of nitrogen to form urea. The urea unit separates oxygen and nitrogen from the urea-containing stream to produce small amounts of oxygen and CO.
_It has a high-pressure scrubber to form a high-pressure nitrogen stream containing ₂ . The method comprises the steps of introducing a high pressure nitrogen stream with compressed air into an autothermal reformer.

At least 1% of the nitrogen fed to the autothermal reformer by the high pressure nitrogen stream in the ammonia / urea integrated process.
Is preferably supplied. The urea unit preferably does not vent the process nitrogen stream to the atmosphere. The high pressure scrubber preferably operates at a higher pressure than the autothermal reformer and directs the high pressure nitrogen stream downstream of the air compressor outlet and into the compressed air conduit upstream of the autothermal reformer. Supply directly. The high pressure nitrogen stream is at least 70 mol% nitrogen, 1 to
15 mol% oxygen, 1-15 mol% ammonia, 1-
Preferably, it contains 10 mol% CO ₂ , less than 3 mol% water and less than 100 ppmv hydrogen.

[0010]

DETAILED DESCRIPTION OF THE INVENTION Recirculating a nitrogen-rich high pressure gas urea synthesis purge stream as feedstock to an ammonia plant (otherwise vented to atmosphere) provides process compression energy required for ammonia synthesis. Saves and eliminates the need to clean the urea purge stream.

1-2, the same numbers refer to similar streams and equipment, but the integrated ammonia / urea process 10 of the present invention uses the urea synthesis process 12 waste stream to supplement the ammonia synthesis process 14. Used as a raw material.

As is well known in the art, it is produced in a continuous process by the reaction of ammonia and carbon dioxide at elevated temperature and pressure. Ammonia and carbon dioxide are combined directly in a liquid ammonia medium to form ammonium carbamate and then the carbamate is dehydrated in a continuous manner to form urea and water.

The ratio of ammonia to carbon dioxide depends on the process used. The well-known Stamicarbon method based on CO ₂ stripping is about 2.8: 1.
Ammonia: carbon dioxide reactant molar ratio is suitable. The Toyo Engineering ACES method based on CO ₂ stripping is about 4.0: 1.
Ammonia: carbon dioxide molar ratio is appropriate. NH
₃ Snapping based on stripping
In the mprogetti) method, the molar ratio of ammonia: carbon dioxide in the feed is about 3.6: 1. At pressures in the range of 14-15 MPa and temperatures of 180-195 ° C, about 50-70% CO ₂ (restricted reactant) conversion is obtained per pass.

As is well known, ammonia is typically produced by catalytically combining hydrogen and nitrogen feedstocks at elevated temperatures and pressures.
Reforming a natural gas feed in the presence of air and steam in a reforming furnace produces an ammonia syngas containing the desired stoichiometric ratios of hydrogen and nitrogen. Carbon dioxide is produced as a by-product of the reforming method. Thus, it can be seen that ammonia production yields the starting materials needed for urea production.

With particular reference to the ammonia method 14 of the present invention, atmospheric pressure air introduced into air compressor 16 through conduit 18 is compressed in two stages. Such air compressors typically use steam power, gas turbine power, or electric motor power (not shown). A portion of what is discharged from the first stage 20 is a urea method 12
Withdraw through conduit 22 for delivery as passivation air therein. The remainder of the first stage effluent is compressed by the second compression stage 24 and sent via conduit 28 to the syngas production unit 26. The oxidant stream in conduit 28 is typically initially preheated by heating coil 30, which coil is typically located in a furnace stack (not shown). The preheated oxidant is removed through conduit 32.

The syngas unit 26 typically comprises a primary reforming furnace 34 and a secondary autothermal reformer 36. A compressed hydrocarbon feed stream 38, typically composed of natural gas, is mixed with steam introduced through conduit 40 and is located through conduit 42 in a radiation chamber (not shown) of furnace 34. Send to reaction coil (not shown). The furnace 34 preheats the hydrocarbon (methane) feed stream and reforms it in the presence of steam to produce hydrogen, carbon monoxide, and carbon dioxide.

The effluent stream from furnace 34 is sent via conduit 44 to an autothermal or secondary reformer 36 for further reforming reactions. However, before the autothermal or secondary reforming of the primary reformer effluent stream 44, the oxidant (eg, air) stream 32
Add the desired stoichiometric amount of nitrogen as one component.

Although the present invention will be described herein in connection with the synthesis gas process illustrated in FIG. 1 by way of example, the present invention also refers to other synthesis gas production processes, such as Le Blanc.
US Pat. No. 5,011,625 to Shire and Shire
s) et al., heating the primary furnace with the effluent from the autothermal reformer as described in U.S. Pat. No. 4,479,925, which descriptions are incorporated herein by reference. It can also be applied to a manufacturing method such as a method.

In carrying out the present invention, the urea synthesis circulation step 4
The high pressure urea synthesis purge stream withdrawn from 6 through conduit 48 is combined with the preheated oxidant stream 32 and conduit 50
To the automatic thermal reformer 36. Urea synthesis purge stream 48 contains primarily nitrogen and small amounts of oxygen, ammonia, and CO ₂ . Oxygen, nitrogen, and CO ₂ from stream 48 are the usual reactants and / or inerts in reformer 36. The small amount of ammonia present is believed to be converted to nitrogen and hydrogen and does not adversely affect the reforming or shift conversion reactions.

From the automatic thermal or secondary reformer 36 to conduit 52.
The effluent stream withdrawn through is passed through a heat recovery device 54, a CO conversion shift reactor 56 for hydrogen, a CO ₂ recovery device 58, a methanation device 60 and residual CO, CO
_2. Remove water and other unwanted constituents.

The thus completed syngas stream is introduced through conduit 62 as make-up syngas to ammonia synthesis cycle 64. In the example ammonia synthesis method illustrated in FIG. 1, the makeup syngas stream 62 is compressed by a two-stage ammonia synthesis compressor 66. However, prior to compression, the makeup syngas stream 62 is combined with the hydrogen stream 68 separated from the ammonia synthesis recycle purge stream 70 by the ammonia purge gas hydrogen recovery unit 72.

The effluent gas from the first compression stage 74 is combined with the ammonia recycle gas introduced through conduit 76. The combined ammonia syngas stream is then compressed by the second compression stage 80 to the operating pressure of the ammonia converter 78. The effluent gas from the ammonia converter 78 is introduced into the low temperature ammonia recovery device 84 via conduit 82. The syngas separated from the ammonia product is recycled through conduit 86. However, the purge hydrogen recovery device 72
The purge stream removed through conduit 70 to feed The hydrogen-poor purge stream 88 is withdrawn from the hydrogen recovery system 72 and used as fuel gas. The ammonia feed stream is sent to the urea plant 12 via conduit 90.

It will be appreciated that the present invention is not limited to the conventional process of ammonia synthesis described above. Other processing mechanisms can also be used. Other examples of ammonia synthesis methods are described in US Pat. No. 4, Mandelik et al.
568,530, U.S. Pat. No. 4,568,531 to van Dijk et al., And Benner.
, US Pat. No. 4,568,532, the disclosures of which are hereby incorporated by reference. Further description of ammonia converter design and catalyst composition can be found in US Pat.
163,775, U.S. Pat. Nos. 4,122,040 and 4,055,62 to McCarroll et al.
No. 8 (their descriptions are incorporated herein by reference).

Returning to the urea process 12, the corrosion passivating air stream 22 is preferably taken from the first stage 20 of the ammonia process air compressor 16 and introduced through conduit 92, as described above. With the carbon dioxide make-up stream,
It is supplied to the urea synthesis circulation step 46. Carbon dioxide replenishment flow 9
2 is preferably supplied as a product stream of the CO ₂ recovery device 58. For example, the carbon dioxide make-up stream 92 to the urea synthesis cycle 46 typically has a maximum hydrogen concentration of about 1.3% by volume (40 ° C., 1.667 KPa absolute).

The combined flow of passivating air and make-up CO ₂ is sent through conduit 94 to a CO ₂ compressor 96. Typically a CO ₂ compressor 96, which is a multi-stage centrifuge.
Compresses the combined stream 94 to a pressure of the order of 15 MPa [absolute pressure (a)]. The compressed CO ₂ containing stream is then withdrawn through conduit 98 and used to remove hydrogen 10
Send to 0. Hydrogen present in the make-up CO ₂ is removed by catalytic combustion in the hydroconverter 100 to a concentration below about 10 ppmv, where a portion of the air provides oxygen for the conversion process. An essentially hydrogen-free airborne CO _{2 make-} up stream is withdrawn via conduit 102.

Compressed CO ₂ / air stream 102 dehydrogenated
Is preferably sent to the stripping heat exchanger 104 operated at the urea synthesis cycle pressure. Stripping heat exchanger 104 removes unreacted ammonia and carbamates from the liquid urea synthesis effluent stream fed through conduit 106. Stripper 104 is typically a vertical falling film heat exchanger, with gas-liquid contact at the surface of tube 108. Stripper 104 is reboiled by process steam supplied to the shell side through conduit 112 and agglomerates are removed through conduit 114. The aqueous urea-depleted aqueous urea product stream is withdrawn from stripper 104 through conduit 116. Urea product stream 116 is then depressurized by pressure reducing valve 118 and fed through conduit 120 to a urea refiner (not shown). The aggregate stream 114 is typically recycled to the boiler.

Make-up carbon dioxide containing small amounts of air and ammonia is withdrawn from the top of stripper 104 and is passed through conduit 122 to a shell and tube carbamate condenser, which is typically operated at urea synthesis cycle pressure. 124
Send to In the carbamate condenser 124, the conduit 126
The high pressure liquid make-up ammonia stream and the carbon dioxide stream 122 introduced through the tube are contacted on the tube side under cooling conditions to produce a condensed carbamate reaction product. At the same time, the heat of carbamate formation passes through conduit 130 to condenser 124.
It is released to the boiler feedwater pumped to the shell side of. The water vapor produced in condenser 124 is withdrawn through conduit 134 for extensive use in the plant. The condensed carbamate effluent stream is withdrawn from the condenser 124 as bottoms and is fed to the urea reactor 136 via conduit 138.

The urea reactor 136 is operated at appropriate urea synthesis conditions and is necessary to facilitate the dehydration of liquid carbamate to urea and water, which is typically a slower reaction than the carbamate formation reaction. It consists of a large vertical container that gives a good residence time. Reactor 136 operates at substantially closed flow conditions with limited internal mixing. The product effluent stream containing aqueous urea and unreacted carbamate is withdrawn from the top of reactor 136 by siphon conduit 140 and passed through conduit 106 to stripper 104 described above.

A vapor purge stream consisting primarily of air introduced into reactor 136 in make-up CO _{2 is} withdrawn from the top of reactor 136 via conduit 142. The purge stream 142 is washed in a high pressure washer 144, which is operated at about the same pressure as the urea synthesis cycle, to substantially remove residual carbon dioxide and ammonia. The high pressure washer 144 has an upper fill region 146 and a lower heat exchange region 148. Stream 142 first passes near upper fill region 146 to directly exchange heat through an explosion dome and then into lower heat exchange region 148 where ammonia and CO ₂ are condensed. Form a carbamate. The heat of carbamate formation is provided by conduits 154 and 15
It is dissipated into the quenched cooling water circulating through the shell side of the heat exchange area 148 through 6. Condensate and non-condensed vapor rise from the lower heat exchange zone 148 to the lower end of the upper fill zone 146. The vapors come into countercurrent contact with the carbamate solution introduced through conduit 147 near the top of fill region 146 as they rise through fill region 146,
Residual ammonia and CO ₂ are substantially removed. For example, stream 147 is obtained as recycled carbamate condensed with the recovery of the urea product from stream 120, but can be any suitable aqueous stream. Purge stream 142, thus substantially scrubbed of residual ammonia and CO _2, is withdrawn via conduit 48, as described above for feed to autothermal reformer 36. Remove the carbamate solution from the bottom of the fill area 146,
Return to urea reactor 136 through conduit 152, through carbamate condenser 124.

Return carbamate stream 152 is preferably drawn from high pressure scrubber 144 and sent to high pressure condenser 124 using an ejector 158 using high pressure liquid ammonia make-up stream 90 as the working fluid. The emitter effluent stream consisting of ammonia make-up stream 90 and returning carbamate stream 152 is sent through conduit 126 to carbamate condenser 124.

In another aspect of the invention, ammonia make-up stream 90 may be introduced into high pressure stripper 104 by conduit 160 to strip CO ₂ and carbamate from urea synthesis effluent stream 106, in which case the snum. CO ₂ / air make-up stream 102 as in the Progetty process
From the hydrogen combustor 100 through conduit 162 to reactor 1
Send to 36.

As can be seen from FIG. 2, the conventional process 20 is used.
As compared with the case where 0 is performed, the purge stream 48 is further cleaned by the intermediate pressure cleaning device 202 at a low pressure, and the purge stream 48 containing air and low concentrations of ammonia and CO ₂ is adjusted to be released into the atmosphere. To do. Purge device 202 uses the plant condensate to further reduce the residual ammonia content in purge gas 48. The purge flow 48 is decompressed by the pressure reducing valve 203 to a pressure up to about 0.4 MPa (absolute pressure) and introduced into the intermediate pressure absorber 204 by the conduit 206. The intermediate pressure absorber 204 has two filling areas 20.
It consists of a vertical shell with 8,210. In the fill region 210, the low pressure purge gas 206 is brought into countercurrent contact with the spray of plant condensate introduced through conduit 212. In the fill zone 208, the effluent gas rising from the fill zone 210 is passed from a condensate cooler (not shown) to the conduit 2
The water flow introduced through 14 is contacted countercurrently. The flow of nitrogen and oxygen depleted in ammonia is in conduit 21.
It is obtained through 6 and discharged into the atmosphere.

The condensed effluent is removed from the bottom of absorber 204 and circulated through conduit 218 to a holding tank to treat residual ammonia, such as by neutralizing with mineral acid. The condensate thus treated is pumped by the pump 220 to the intermediate pressure absorber 2.
04, after cooling with cooling water in the heat exchanger 222, recirculation. All purging devices 202 are preferably excluded in the present invention.

[0034]

The advantages of the method of the present invention are illustrated with reference to the following examples. Example 1500t / day (MTPD) urea plant and 100
The effect of integrating the purge stream 48 from the urea plant high pressure washer 144 with the ammonia plant secondary reforming zone 36 for a 0 MTPD ammonia plant was analyzed by computer simulation. In addition, a standard cost estimation program was run to calculate the cost savings and investment equipment available.

No adverse effect was found on the operation of the secondary reformer 36. Purge recycle stream 48 is approximately 78.8 mol%
Nitrogen, 9.8 mol% oxygen, 8.0 mol% ammonia, 3.1 mol% CO ₂ , 0.3 mol% water, 10 p
It contained less than pmv of hydrogen, which was from the CO ₂ stream 62 after combustion in the hydrogen combustor 100. However, assuming that as much as 100 ppmv of hydrogen remains in the purge recycle stream 48, the combustion of hydrogen raises the temperature of the process air (air to the autothermal reformer 36) up to about 0. It will only rise by 3 ° C. Savings in the ammonia plant include reducing the power consumption of the air compressor 16 by about 3.2%, and circulating cooling of the air compressor power steam (not shown) by reducing the amount of steam required. Reduced water.

There is no adverse effect on the urea plant. Investment equipment savings include the elimination of intermediate pressure absorber 204 and the elimination of accessories such as condensate pumps and coolers, control valves and stainless steam piping. However, the exclusion of the intermediate pressure absorber 204 eliminates the estimated capacity 20 to feed the aqueous ammonia solution from the tank to the atmospheric pressure absorber (not shown) for treating another ammonia containing vent stream.
Requires the addition of a centrifugal pump (not shown) at m ³ / hour.

Table 1 shows the usage cost reduction for one year in the integrated plant of the present invention. Cost savings over the three years is approximately 252,0
It's $ 00. The capital cost savings are given in Table 2. The total capital savings was estimated to be $ 616,000.

[0038]

[Table 1] a-$ 2.5 / MMBTU b-$ 0.05 / KWH c-$ 0.5 / MT d-$ 0.03 / m ³

[0039]

[Table 2]

The ammonia / urea integration method of the present invention has been illustrated by the foregoing description and examples. The above description is not intended to be limiting. This is because many modifications will be apparent to those skilled in the art upon reading the description. All such changes that come within the scope and spirit of the claims are within the scope of the claims.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an ammonia / urea integrated process of the present invention showing a high pressure urea synthesizer purge stream recycled to an air inlet stream of an ammonia syngas autothermal reformer.

FIG. 2 is a schematic diagram of a conventional urea process showing the intermediate pressure absorber and associated equipment used to reduce the ammonia concentration in the urea synthesizer purge stream for exhaust to atmosphere.

[Explanation of symbols]

12 Urea Plant 16 Air Compressor 26 Syngas Production Device 30 Heating Coil 34 Primary Reformer (Furnace) 36 Secondary Automatic Thermal Reformer 46 Urea Synthesis Circulation Process 54 Heat Recovery Device 56 Shift Reactor 58 CO ₂ Recovery Device 60 Methane recovery device 66 Compressor 72 Hydrogen recovery device 78 Ammonia converter 84 Low temperature ammonia recovery device 96 CO ₂ compressor 100 Hydrogen removal device 104 Stripping heat exchanger (stripper) 124 Condenser 136 Urea reactor 144 High pressure washer 158 Discharger 202 Purging device 204 Absorber 219 Holding tank 222 Heat exchanger

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Meguji N. 1107 (72) Inventor Richard Bruce Straight, Sugar Land, Texas, USA United States 5615 Lawn Cedar Drive, Kingwood, Texas, United States 5615

Claims (8)

[Claims] 1. A primary reformer, an automatic thermal reformer, a shift converter, and a CO ₂ removal device, which reacts a hydrocarbon feedstock with steam and air to produce a CO ₂ stream and hydrogen. Ammonia synthesis gas device for forming a syngas make-up stream consisting of nitrogen, mixing a recycle stream and said syngas make-up stream to form an ammonia converter feed stream, and directing the ammonia converter feed stream to the ammonia synthesis reactor To the effluent from the synthesis reactor and to recover a purge stream from the effluent stream to form a recycle stream, an ammonia converter having a synthesis circuit, the CO ₂ stream and the ammonia stream. Is a urea apparatus for forming urea by reacting and with a passivation effective amount of oxygen and a small amount of nitrogen at a relatively high pressure of greater than about 14 MPa. Was separated, introduced into small amounts of oxygen, urea unit having a high-pressure scrubber to form a high pressure nitrogen stream from about 14MPa containing CO ₂ and ammonia, and autothermal reformer high pressure nitrogen stream with compressed air Ammonia / urea integrated plant with a conduit for operation. 2. The plant of claim 1, wherein the high pressure nitrogen conduit is in direct communication with a compressed air conduit downstream of the air compressor, and the pressure in the high pressure nitrogen conduit is greater than the pressure of the compressed air conduit. . 3. The urea system according to claim 2, wherein the urea system does not have ammonia removal equipment for treating the high pressure nitrogen stream and does not have an exhaust vent to the atmosphere for nitrogen from the high pressure washer. Plant. 4. A method for integrating the operation of an ammonia plant and a urea plant, comprising a primary reformer and an autothermal reformer, a shift converter, and a CO ₂ scavenger, and a hydrocarbon feedstock. An ammonia syngas device for reacting steam and air to form a CO ₂ stream and a syngas make-up stream consisting of hydrogen and nitrogen; mixing a recycle stream with said syngas make-up stream to feed an ammonia converter Forming a stream, feeding an ammonia converter feed stream to an ammonia synthesis reactor, recovering an ammonia stream from the effluent from the synthesis reactor, recovering a purge stream from the effluent stream and forming a recycle stream. Ammonia converter having a synthesis circuit; the CO ₂ stream and the ammonia stream are reacted at relatively high pressure in the presence of a passivating effective amount of oxygen and a small amount of nitrogen to form urea. A urea unit for producing oxygen and nitrogen separated from the urea-containing stream and removing a small amount of oxygen, CO
A urea unit having a high-pressure scrubber at a pressure higher than 14 MPa for forming a high-pressure nitrogen stream at a pressure higher than 14 MPa containing ₂ and ammonia; and introducing the high-pressure nitrogen stream with compressed air into the autothermal reformer Ammonia / urea integrated process with steps. 5. The ammonia / urea integrated process of claim 4, wherein the high pressure nitrogen stream supplies at least 1% of the nitrogen supplied to the autothermal reformer. 6. The ammonia / urea integrated process of claim 5, wherein the urea device does not vent the process nitrogen stream to the atmosphere. 7. A high pressure scrubber is operated at a pressure higher than that of the automatic thermal reformer, and high pressure nitrogen is introduced into a compressed air conduit downstream of the outlet of the air compressor and upstream of the automatic thermal reformer. Ammonia / urea integrated process according to claim 4, wherein the stream is fed directly. 8. The high pressure nitrogen stream comprises at least 70 mol% nitrogen, 1-15 mol% oxygen, 1-15 mol% ammonia, 1-10 mol% CO ₂ , 3 mol% or less water, 1.
8. The ammonia / urea integrated process of claim 7, comprising less than 00 ppmv hydrogen.